Examining small areas in two images captured by a stereoscopic optical system to detect parts in which the same object appears, calculating the offset of the corresponding positions, and calculating the distance to the object by the principle of triangulation is a previously proposed technique.
For example, the gradation correction apparatus described in Patent Reference 1 performs stereo matching by calculating a city-block distance between small areas in each of two images to obtain their mutual correlation and identify corresponding small areas. The gradation correction apparatus then carries out distance measurements by obtaining three dimensional image information (a distance image) in which the range information obtained from the pixel offsets (parallaxes) arising from the distance to objects is quantified.
The imaging apparatus described in Patent Reference 2 combines images captured by a plurality of cameras, including a super wide angle camera having a field of view of substantially 180°, and displays, on a display means, a multiple-perspective video and a bird's eye view video (with a single viewpoint) from above a vehicle. This imaging apparatus accordingly enables the driver to recognize the situation around the vehicle.
In a position detection apparatus that detects the position of an object to be measured from a pair of images obtained by a stereoscopic image input means, the imaging apparatus described in Patent Reference 3 measures the distance to a point illuminated by light after executing distortion corrections on the left and right image data.